Sunjammer is one of three of NASA’s technology demonstration missions. For launch in 2014, a small package will go into orbit around the Earth and will unfold into a huge sail measuring 400m x 400m. The goal is to show that the technology can be built, and can operate as designed. If successful, bigger missions will follow with additional goals. The sail will rely on photons hitting its vast sail to push it around just as wind does for sails on boats on Earth. The hope is that by tilting the sail, it will be able to tact, manoeuvre and navigate to different positions. Jonathan Eastwood’s team is designing a magnetic detector. A solar sail could provide advance warning of whether a coronal mass ejection heading towards the Earth would cause a geomagnetic storm.

Transcript

Robyn Williams: Later this year, if you are a keen-eyed observer, say using a telescope looking somewhere near the Sun, you may, with luck, see a gigantic sailed spacecraft, as big as the Olympic Park or nearly, drifting in orbit. It's called the Sunjammer and it will carry experiments from places such as Imperial College in London where Jonathan Eastwood lectures in physics.

Jonathan Eastwood: Sunjammer is a solar sail mission, it's a technology demonstration which is going to take place next year.

Robyn Williams: What time next year, 2014?

Jonathan Eastwood: October, November.

Robyn Williams: Is NASA going to put it up?

Jonathan Eastwood: It is being funded by NASA, it's going to launch from Florida. It is actually built by a company called L'Garde in California.

Robyn Williams: And what is the Sunjammer name signifying?

Jonathan Eastwood: This is an interesting historical point; 'Sunjammer' is the name of a short story by Arthur C Clarke where he describes a sort of interplanetary Formula One race involving solar sails, and so it was that story that inspired the name of the mission.

Robyn Williams: And what will the Sunjammer actually be like? Jamming sunlight?

Jonathan Eastwood: Reflecting sunlight. It will start off around the size of a washing machine or something like this, and then it will unfurl and deploy an enormous solar sail, which is basically a very, very thin sheet of plastic coated with metal to make it reflective like a mirror, and this will unfurl to a size of about 400 metres by 400 metres, enormous and huge, but you need it to be that big to get the pressure of the sunlight to make a noticeable effect.

Robyn Williams: The pressure of the sunlight, the solar winds, so to speak, will be enough to make that vehicle move.

Jonathan Eastwood: The thing we are talking about here is the pressure of the photons, the light itself that comes from the Sun. And so literally by the photons bouncing off the reflective surface, that pushes the sail, and so you can use that just like you would a yacht on the ocean to use the wind to tack in different directions. It's the same thing that you do in space.

Robyn Williams: So presumably the Sunjammer is not going to just sail itself serenely around the system for a bit of fun, it is out there to seek something; what?

Jonathan Eastwood: Actually in the first instance its goal is to demonstrate that it can be navigated and moved where you want it to go. In this case what we want to do is go towards the Sun and then kind of hover between the Sun and the Earth, and from there measure things that come from the Sun.

Robyn Williams: But how can you harness the motive power, you know, the photons, which presumably are coming away from the Sun, how can you use them to go towards the Sun?

Jonathan Eastwood: That's a very good question. The thing you have to remember is in space that you are always going round. So the planets are going round the Sun, and if you have a satellite that's going around the Sun, so everything is going round. And actually if you speed up or slow down then you fall in or you move away. And so actually by tilting the sail so that you are not just directly reflecting but you reflect at an angle, then actually you can go pretty much anywhere you want if your sail is big enough.

Robyn Williams: You can go tacking.

Jonathan Eastwood: Exactly, and so some of the early plans for what Sunjammer will do, you'll see that it starts off going in one direction and it actually turns around and goes back.

Robyn Williams: So it's seeing whether it can be done, as if there is a follow-up which is going to be in some ways the real experiment. What will that be?

Jonathan Eastwood: The reason that there is this technology demonstration is because there are lots of ideas of things you could do with solar sails, but you have to demonstrate that it can be done first. And so the engineering required to pack a sail into a very tiny volume and then deploy it into one big thin enormous sheet is not easy. And so that's what the goal of this mission is, to actually show that all of this will work.

In terms of applications afterwards, there are various ideas for using it. You can have the spacecraft effectively hover in different places near the Earth, so for polar communications, or much more esoteric things, one idea is that you could build a sail and use it to actually power a satellite to leave the solar system and go into interstellar space, and there is a mission idea called the interstellar probe that would use that.

Robyn Williams: Jonathan, what are you doing here at Imperial as part of this Sunjammer mission?

Jonathan Eastwood: We are building a science experiment called a magnetometer which measures magnetic fields, and we are involved in Sunjammer as a kind of end user because what we are going to do is use Sunjammer as a platform to measure the magnetic field created by the Sun in space in the so-called solar wind. And this is a stream of particles continually emanating from the Sun going into space, it's very, very rarefied, but it's still there and it's very important because things that the Sun generates in its magnetic field and particles and plasma can travel through space and hit the Earth and create space weather. And so our goal is to demonstrate that you could put this instrument on the solar sail and demonstrate that it could be used as part of a space weather warning system.

Robyn Williams: So will it go up next year or later when the system is proven?

Jonathan Eastwood: Well, we will go up on the Sunjammer…

Robyn Williams: So there's only one shot?

Jonathan Eastwood: Yes, so there's only one spacecraft at the moment. If it's successful then we would hope that that would then provide a blueprint pathway to doing a bigger, better version which could then be applied to all these other things.

Robyn Williams: And what's your magnetometer like? Tiny, fragile?

Jonathan Eastwood: It's very small actually, that's why we are involved. Because sunlight is so weak in the pressure it provides, you want your spacecraft to be very light. And so we were approached because we've built a very small magnetometer which is actually using a solid-state sensor, so it's kind of like the magnetometer…these exist in mobile phones now and so on. And that means that the sensor itself is about an inch on a side in the box and then that sits on a boom a bit away from the spacecraft and measures the magnetic field.

Robyn Williams: It's amazing when you think of the Sun producing such obvious turbulence. We see the storms, we see the space weather, the interference with various instruments. But is there enough activity from the Sun possibly to be a threat to a delicate vehicle like that?

Jonathan Eastwood: The spacecraft is designed in the knowledge of the sorts of environments we expect it to encounter, and we designed it to last a certain number of years. So in that regard it should last just fine, yes.

Robyn Williams: Jonathan Eastwood lectures in physics at Imperial College in London, and Sunjammer goes up, as you heard, later next year around October.

Guests

Jonathan Eastwood

Lecturer and research fellowDepartment of PhysicsImperial CollegeLondon